All articles starting with P

Phase field crystal model

The phase field crystal model is a continuum simulation method resolving atomic-scale crystal structure and defects over diffusive timescales, proposed by Elder and colleagues in 2002.

A phase field model is a continuum simulation method that represents evolving microstructures, such as growing dendrites, by continuous order-parameter fields rather than explicitly tracked interfaces.

Phase field simulation

Phase field simulation is a computational modeling method that represents evolving microstructures, such as solidifying dendrites and coarsening grains, using continuous order parameter fields with diffuse interfaces instead of explicitly tracked boundaries.

Oct 22, 2026

Phase H

Phase H is a dense hydrous magnesium silicate, MgSiO4H2, stable at lower-mantle pressures and regarded as the deepest mineral able to carry subducted water into the deep mantle.

Phase I/II trial

A Phase I/II trial is a clinical trial design that combines dose escalation and safety evaluation with early evidence of treatment efficacy, aiming to find the optimal biological dose.

Phase II/III trial

A Phase II/III trial, often called a seamless or adaptive seamless design, combines Phase II and Phase III objectives in one protocol, selecting doses at an interim analysis while controlling type I error.

Phase inversion

Phase inversion is a membrane fabrication method that converts a homogeneous polymer solution from liquid to solid by controlled demixing, producing the porous separation membranes behind most commercial products.

Oct 3, 2026

Phase IV

Phase IV (1974) is Saul Bass's only feature film, a science fiction horror work in which cosmic radiation gives an Arizona ant colony collective intelligence; it flopped, won Trieste's Grand Prix, and its cut ending resurfaced in 2012.

Phase IV trial

A Phase IV trial, also called Phase 4, is a study of a drug after marketing approval, measuring safety, effectiveness, and optimal use in broader patient populations.

Phase margin

Phase margin is the additional phase lag, in degrees, that a feedback loop can tolerate at its gain crossover frequency before becoming marginally stable, a classical stability margin.

Phase matching

Phase matching is the condition in nonlinear optics where the wave vectors of interacting light waves are balanced, allowing frequency conversion in crystals to add coherently and efficiently.

Phase modulation

Phase modulation (PM) is a method of encoding a message signal on a carrier wave by varying the carrier's instantaneous phase, used in analog and digital systems.

Phase noise

Phase noise is the random fluctuation of an oscillator's phase, reported as a spectrum in dBc/Hz; it degrades clock signals and is the frequency-domain counterpart of timing jitter.

Phase of the wave function and gauge transformations

The phase of the wave function is the angle of its complex value; global phase is unobservable, while local phase changes tie quantum mechanics to electromagnetism.

Oct 10, 2026

Phase One trade deal

The Phase One trade deal was the 2020 US–China agreement that paused the tariff war in exchange for $200 billion of additional Chinese purchases, with purchase targets that went unmet.

Phase problem

The phase problem is the loss of phase information in diffraction experiments, where detectors record intensities but not phases, leaving crystal structures unsolvable without recovery methods.

Phase reduction

Phase reduction is a mathematical technique that replaces a high-dimensional model of a weakly perturbed limit-cycle oscillator with a single phase variable, making synchronization of neural, chemical, and circadian oscillators tractable.

Phase retrieval

Phase retrieval, also called phase recovery, reconstructs a signal from the magnitude of its Fourier transform when detectors record only intensity, as in diffraction imaging, astronomy, and radar.

Phase rule

The phase rule, or Gibbs phase rule, is the thermodynamic relation F = C − P + 2, formulated by Josiah Willard Gibbs in the 1870s.

Oct 21, 2026

Phase Separation

Phase separation, especially liquid–liquid phase separation (LLPS), is the demixing of a homogeneous mixture into dense and dilute phases; in cells it forms biomolecular condensates, membraneless organelles linked to disease and materials design.

Phase shift

In quantum scattering theory, the phase shift δℓ(k) is the angle by which a scattered partial wave is rotated relative to the wave propagating with no potential.

Phase space

Phase space is the space of all possible instantaneous states of a physical system, where a single point specifies the complete state; for n degrees of freedom it is 2n-dimensional.

Phase space reconstruction

Phase space reconstruction is a nonlinear time series analysis method that rebuilds a dynamical system's attractor from a single scalar signal using time-delayed coordinates, justified by Takens' embedding theorem.

Phase stability (accelerator physics)

Phase stability, conceived independently by Vladimir Veksler in 1944 and Edwin McMillan in 1945, is the principle that keeps circular accelerator particles bound to a fixed RF phase.

Phase transition

A phase transition, also called a phase change, is a change in the nature or number of phases of a system as temperature, pressure, or an applied field varies.

Phase unwrapping

Phase unwrapping is the computational recovery of an unambiguous phase field from measurements known only modulo 2π radians, central to SAR interferometry, digital holography, and fringe projection.

Oct 21, 2026

Phase Variation

Phase variation: random, frequent, reversible ON/OFF switching of bacterial contingency genes via simple sequence repeats, DNA inversion, or DNA methylation, enabling immune evasion, niche adaptation, and phasevarion-regulated virulence in pathogens.

Phase velocity and group velocity

Phase velocity and group velocity are two distinct speeds of a wave: the speed of a single crest and the speed of a wave packet's energy.

Oct 22, 2026

Phase-change artificial neuron

A phase-change artificial neuron is a hardware neuron device using a phase-change material such as GST to emulate the spiking behavior of a biological neuron.